The invention relates to a process for producing a three-dimensional structure.
Such structuring methods are used in particular for producing micro- or nanostructures, prototypes (e.g. so-called “rapid prototyping”) or when producing workpieces having specific shape requirements, e.g. for experimental purposes and in areas in which great freedom of design is desired.
Structuring devices which have a predefined principal direction of the structure entry are often utilized in this case. The principal direction is generally predefined by constructional dictates, e.g. by the preferred direction of a structuring electron beam, by the optical axis of a laser optical assembly, by the direction of a material build-up beam of a 3D printer or by the mechanical spindle of a processing tool that is controllable in three spatial directions.
The structuring device generally also has a writing region that is delimited by constructional dictates. A structuring or a structure entry can be effected only in this delimited spatial region. In this case, the predefined writing region is often smaller than the overall structure to be produced overall. Therefore, in so-called “stitching methods” the entire structure is decomposed into a multiplicity of partial structures which match the writing region of the structuring device and are written successively.
Stereolithography methods are known from U.S. Pat. No. 4,575,330 A1 or U.S. Pat. No. 5,247,180 A, wherein a desired structure is built up from block-like partial structures or layer by layer in a bath of liquid lithography material (e.g. a photopolymer) by targeted exposure using a writing beam. For this purpose, the writing beam, by means of local exposure, in each case polymerizes structure blocks in a layer at the surface of the bath of lithography material with a desired pattern. By a carrier substrate being lowered step by step in the bath of lithography material, the structure is then built up layer by layer.
In this case, there is the problem that partial structures that have already been defined can disturb the introduction of a partial structure to be written subsequently. By way of example, in the case of block-like decomposition of the structure, individual sections of the structure blocks that have already been defined can shade or obstruct the writing beam during the definition of a following partial structure. This can lead to structuring faults. It is often necessary, therefore, to decompose the desired structure into a very large number of partial structures, which can lead to long process times for the decomposition into the partial structures and for the writing of the partial structures.